Origen

You can smoke cannabis (late 18th century), or, more legally, make canvas out of its fibre. The versatile cannabis plant, also known as hemp (ultimately from the same root), gives its name to the fabric, as both come from Latin cannabis. To win a race or competition by a canvas is to win it very narrowly. The canvas here is the tapered front end of a racing boat, covered with canvas to keep water out. In the early16th century the verb canvass meant ‘to toss someone in a canvas sheet’, as a punishment or as part of a game. Other early meanings included ‘to beat’ and ‘to criticize severely’. This led on to the idea of discussing an issue, and then to proposing something for discussion. Finally, the word acquired the meaning ‘to seek support’, as in ‘to canvass for votes’ at an election.